It has been proposed the past to protect orchards and the like by use of acoustical, optical or ultrasonic deterrent devices which were stationary located in the plots to be protected in order to repel bird flocks and similar vermins from such plots.
However, it has been observed, when utilizing such stationary optical systems, which at best may be moved by the prevailing wind, that the effectiveness after only short duration after installation of such system is greately decreased since the animals became accustomed to the stationary silhouettes, shapes and other deterrend devices.
When using simply strips of material such as cloth, reflecting foil or the like suspended from supporting ropes or wires, the immobility of such strips of material during calm periods does not provide a deterrent at all.
As well, it has been proposed in the past to cover such plots with nets or similar protective webbing against attack by bird flocks. This approach is limited, however, to relatively small plots since the cost of installing and operating a system according to this method would be prohibitive for large plots.
Furthermore, it has been proposed to protect such plots with acoustical systems such as recordings, played back at high volume, of distress and warning calls of the species against which attack the field or plot was to be protected. As well other noise makers including cap gun noises and the like explosive have been tried in the past. Such methods do add a certain excess of noise to the surrounding neighborhood and it has been found that the deterrent effect of such methods is reduced in a very short period of time after installation. Thus, as the animals become accustomed to the various sounds including recorded distress calls of their own species, they will increasingly ignore such deterrent measures, moreover, when these signals are repeated at regular intervals.
Also known in the art are devices which carry, suspended on carrying ropes, wires or other support means, the scarecrow device or devices. The support means can then be moved in a predetermined sequence in a given motion, i.e. up or down or to and fro.
When employing such devices which have been used in large plots or fields, irrespectively of the particular scarecrow device utilized, i.e. acoustical or optical, the disadvantage arises that the fringes, primarily the corners of rectangular or square plots, are not as effectively guarded against the damage by the animals. As well, in the vicinity of trees and brushwood, providing some cover for the animals, these devices have not been effective in preventing loss due to animal damage and destruction.